There are conventional piezoelectric lighters as portable igniters. Such lighters each include a gas tank at one end of a relatively long body. A valve mechanism is provided at the top portion of the gas tank for opening or closing a gas path that extends from the valve mechanism towards a nozzle formed at the tip of the valve mechanism. Also, a piezoelectric mechanism is provided for generating discharge current in ganged relationship with a lever type manual actuation button operable from the exterior of the lighter. A lever mechanism is provided for opening the valve mechanism in connection with the current generation operation of the piezoelectric mechanism. Actuation of the actuation button opens the valve mechanism for opening the gas path to emit fuel gas from the nozzle. At the same time, the piezoelectric mechanism generates discharge current, which flows as a spark between a discharge terminal disposed near the nozzle and the nozzle tip for igniting the fuel gas emitting from the nozzle. Lighters also exist where a separate manual actuator is used to release fuel gas and then the actuation button is used to generate an ignition spark.
Commonly, a slidable actuation button is positioned at the tip portion of the piezoelectric mechanism so that when it is pushed in the longitudinal direction of the lighter, the piezoelectric mechanism is also pushed for simultaneous gas release and piezoelectric actuation. Also known is an actuation button for pushing in a direction at an angle with respect to the longitudinal direction of the lighter, with a link connecting motion of the actuation button to the piezoelectric mechanism.
The lighters described above can be in the form of cigarette lighters with nozzles adjacent the release valve or utility lighters where the nozzle tip is spaced from the valve to provide a flame at a distance from the user. Also, such lighters may include a power source and a spark coil circuit much like those used on modern kitchen gas stoves.
It is known in lighter with actuation buttons that as increased actuation load makes the lighter more difficult to inadvertently ignite by all users especially people too young to have knowledge of proper use and an appreciation of danger of the open flame such lighters produce. U.S. Pat. No. 5,971,751 discloses a piezoelectric ignition lighter including a coil spring and a resilient member serially arranged inside an actuation button. The ignition actuation mechanism is configured such that forces to resist actuation are generated by the coil spring until it is fully compressed. Thereafter, the compression of the resilient member abruptly provides actuation-resisting forces at a much higher spring rate so that much higher forces are required to continue to move the actuation mechanism. Adults feeling the abrupt change in spring rate are sometimes fooled into believing that the piezoelectric mechanism has been fully depressed, does not produce a spark and that therefore is defective. Also commercially available are lighters having heavier spring load than normal inside a piezoelectric mechanism, thereby increasing actuation load to such level that young users have difficulty in producing an ignition.
Just like cigarette lighters, utility lighters are safer if they are designed so that people without the mental capacity to appreciate the danger of an open flame have difficulty actuating them. The conventional technique of increasing the final actuation load used in the ignition actuation mechanism for piezoelectric ignition lighter could be applied to a utility lighter. However, the conventional ignition actuation mechanism for lighter is constructed to increase the actuation load at a uniform spring rate from an initial preload over the entire actuation stroke of the piezoelectric mechanism. In other words, the actuation Load is heavy from the initial stage of ignition operation, which is not easy to operate even for adult users. The same problem remains when the technique is applied to a utility lighter.
It is therefore an object of the present invention to provide an ignition actuation mechanisms for utility lighters capable of producing light actuation loads during the initial actuation stage and increasing the actuation load abruptly immediately before discharge. In this way, it is possible to restrict operation by children while providing easy operation by adult users.